Quantum computers

John Clark (jonkc@worldnet.att.net)
Mon, 16 Aug 1999 02:24:23 -0400

Hash: SHA1

>Patrick Wilken wrote: [crypto is secure] presumably only until we develop
>reasonable quantum computing. How long is that going to take? 20years? Are
>their any encryption schemes that will hold up to a QCs assault?

>Spike Jones <spike66@ibm.net>
>Actually, yes. The crypto guys can make their codes arbitrarily secure
>simply by making the keys arbitrarily long. With QC, the length of the
>keys would make them a pain in the ass, of course. Even if we continue
>Moore's Law-ing for the foreseeable future, given longer keys, computers
>will not be able to overpower the algorithm found in PGP. spike

If a practical quantum is ever built PGP is dead, just making the key larger is a lousing proposition, you'll never keep up. When a conventional 64 bit single processor computer performs an operation, it does it on one 64 bit number at a time. When a 64 bit (actually a 64 qubit) single processor quantum computer performs an operation, it does it on all 64 bit numbers at the same time, all 2^64 of them, more than a billion billion, and any increase in the number of qubits the computer can handle will increase it's already astronomical power exponentially.

However you could still communicate privately if you used quantum cryptography. I written a post on quantum cryptography before, if anybody's interested I'll try to dig it out and re-send it.

Hal said that a working quantum computer would not prove that the many world interpretation is correct and he's right, but it would make it much more popular. You'd have to understand such a beast pretty well to program it and the many world way would probably be the clearest way to think about it.

John K Clark jonkc@att.net

Version: PGP for Personal Privacy 5.5.5

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